Automatic telephone system



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I6 w//vF/Pfo P0 wia Patented Aug. 31, 1954 AUTOMATIC TELEPHONE SYSTEM Winfred T. Powell, Rochester, N. Y., assignor to Stromberg-Carlson Company, a corporation of New York Original application August 22, 1947, Serial No. 770,119. Divided and this application February 9, 1951, Serial No. 210,126

(el.v 179-18) 16 Claims. l

This invention relates to switching systems and it more particularly pertains to automatic telephone systems.

The present application is a division of my copending application Serial No. 770,119, led August 22, 1947. y

It is an object of the present invention to provide an automatic marker transfer circuit, whereby circuit means are effective for transferring from one common marker to a reserve common marker in response to a fai-lure of the regular common marker circuit. For example, the regular common marker is used during the normal operation of the system, then in the event of a failure of either the tens or units portion of the marker circuit a time delay circuit will be effective for operating and locking a switching relay, which in turn transfers all of the marker wires from the regular marker to the reserve marker and sets up an alarm condition for indicating that the reserve marker is being used in place of the regular marker. Then in the event of a failure of the reserve marker, the time delay circuit functions to transmit a major alarm to the remote ofce. In the event that the trouble condition of the reserve marker clears up, then the reserve marker is again placed into service. The regular marker is cut back into service by the manual operation of a key, upon the visit to the remote once of a repair man.

Other objects, purposes, and characteristic features of the present invention will be in part obvious from the accompanying drawings and in part pointed out as the description thereof progresses.

In describing the invention in detail, reference will be made to the acompanying drawings in which like reference characters designate corresponding parts and in which Figs. 2 to 16, inclusive, when arranged in accordance with the diagram of Fig. 17 and with correspondingly identified lines in alignment, disclose a sufficient amount of the detailed circuits for an understanding of the various features provided by the present invention.

Fig. 1 is a single line block diagram illustrating in a conventional manner the layout of the system, with the various circuit elements interconnected in the suboiiice and having access to two-way trunks tothe main office, these two-Way trunks also being accessible to calls originating in the main office and terminating in the illustrated subofce.

For the purpose of simplifying the drawingsv parts and circuits consitituting the embodiment of the invention have been shown diagrammatica-lly and certain conventional illustrations have been employed, the drawings having been made more with the purpose of making it easy toI understand the principles and mode of operation than with the idea.' of illustrating the specic construction and arrangement of parts that would be employed in practice. For example, the various relays and their contacts are illustrated in a conventional manner, with all of the contacts associated with a particular relay being indicated as controlled by this relay by means of a dashed line associating the relay coil with its contacts. Reference characters have been applied to the relays and to certain conductors which suggest a circuit function. For example, CO indicates a cut-olf relay, LO indicates a lock-out rleay, ITF indi- Cates a rst transfer relay, ZTF indicates a second transfer relay, IUF indicates a first units finder relay or conductor, 2UF indicates a second nder relay or conductor, etc. Slow release relays are indicated by the usual cross-hatched section applied to the lower part of the block indi'- cating the relay coil. Slow operate relays have a solid heavy line applied to the upper portion of the block illustrating the relay coil. Alarm and time release relays and circuits, usually provided in systems of this type have been omitted from the present disclosure, since these circuit elements may be applied in any approved manner to provide the circuit operation required, such for' example as disclosed in Powell Patent 2,325,877.

It is believed that the invention will be best understood by explaining the operation of the various circuits when a call is originated from a particular calling line, for example line No. 1l to which substation A is connected, as illustrated in the upper left hand portion of Fig. 2, the call being directed to a wanted substation by dialing `a five-digit number for selecting substation B which may be connected'to the terminals of the line connector relays illustrated in Fig. 16.

In describing the operation of the present invention, it will be particularly pointed out how the circuits function when the calling subscriber dials the rst two digits of a number associated with the main oice, for example, office B of Fig. l and it will then be explained how the circuits function when the first two digits dialed correspond to stations associated with the suboice, for example oi'ce A illustrated in Fig. 1. Referring to Fig. 1, it will be assumed that the stations connected to the system of omce A are six-digit numbers, the first two digits (74 for example) 3 corresponding to the suboce A, these two digits being dialed from any oice in the network to select the equipment in the suboice. The third digit (6 for example) operates the first selector repeater or the incoming selector to the sixth level for selecting a connector of the group located in the subofilce. Level 8 of the incoming selectors and the rst selector repeaters are multipled to level 6, so that all connectors may be selected by dialing number 8 for the third digit as well as by dialing No. 6 for the third digit. This multiple arrangement of levels 6 and 8 is for the purpose of marking or indicating coin box or paystation lines to the distant operator. For example, paystation lines may all be assinged No. 8 for their third digit and since the dialing of this number for the third digit operates the equipment the same as by dialing No. 6 for the third digit, this assignment does nothing more than indicate to the toll or distant operator that the called or calling line is a coin box line.

As indicated by the dashed line connecting the last or No. 12 combination connector in with the group of the first 11 connectors, this combination connector is normally selectable from the third level of the incoming selectors only and since this number is known only to the test clerk, it is used for seizing the combination connector for test purposes from the test desk. As above mentioned and as indicated in Fig. 1, this No. 12 combination connector is used as a regular connector for regular calls only when all of the other eleven connectors are busy, thus keeping the No. 12 combination connector unblocked for use by the test desk as long as there is at least one regular connector idle for regular service.

It is believed that the operation of this system will best be understood by describing the various types of calls. The layout shown in Fig. 1 indicates that there are 1GO lines in the subofce, any one of which may be connected to any idle nder upon the initiation of a call and may be selected by any connector on a terminating call. For convenience in describing the operation of this system, it will be assumed that there are line finders numbered from 1 to 10 associated with ten corresponding local rst selector repeaters, numbered from 16 to 25. The 100 lines operate through a regular marker and a finder allotter for allotting the line nders for use in extending originating connections. As indicated by the dashed lines, there is a reserve marker associated with the regular marker, this reserve marker being brought into service only when the regular marker fails. The first selector repeaters have access to two-way trunks leading to oice B each of these two-way trunks terminating in a two-way repeater in office B. These two-way repeaters are selected from level No. '74 in ofce B for calls from oice B to oiiice A and are associated with corresponding incoming selectors in ofiice B for handling incoming calls from oiice A. Since the features of the present inventicn relate to the circuits in office A and since the two-way trunk operation, including the equipment illustrated in ofce B, is assumed to be that in a standard automatic telephone system, which may be of the well-known step-bystep type, the operation of the equipment in oce B is not shown and need not be explained in detail.

There is an incoming selector in ofce A normally associated with each two-way trunk for handling calls from office B to oice A, these incoming selectors being numbered from 1 to 15.

The eleven regular connectors are numbered 1 to 11, while the combination connector is No. 12. It will be found from the following description that the numbering of these various units as indicatedis convenient for explaining the operation of the various allotter circuits.

Assuming a call to be originated from station A, line II of Fig. 2, the closure of the line causes the operation of line relay LR over a circuit which may be traced from (-I-), break contact of all trunks busy relay ATB of Fig. 4, conductor ATB, break contact of cut-oir relay CO of the line circuit, upper winding of line relay LR, tip line conductor T, substation A, ring line conductor R, break contact of relay CO and lower winding of relay LR to The operation of relay LR closes a circuit for operating the tens marker relay, in this example ITLOI because the tens digit of the calling line is No. 1, which extends from (-I-) make contact of relay LR, break contact of relay CO, common tens digit conductor No. 1, break contact of switching relay SW, winding of relay ITLOI, break contact of relay ITLO I, conductor 'II, break contact of relay ITLOU, through a series circuit including other ITLO relays (not shown), break contact of relay ITLO2, break contact of relay ITLOI and resistor IRS to Relay ITLOI operates and closes a locking circuit for itself from resistor IRS, make contact and winding of relay ITLOI and over the remainder of the previously described circuit to at a front contact of relay LR. The operation of relay ITLOI opens up the above described series circuit to thus preventing the operation of any other ITLO relay while the rst operated relay of this group remains in its operated condition. It will be observed from the marker circuit that the operation of any one of these ITLO relays is effective, when a call is originated from a line with a corresponding tens digit, for locking itself operated and for of all lines having tens digit No. 1, make contact of relay LR, break contact of relay CO and lower winding of relay LO to The operation of relay LO now closes a circuit for operating the units lockout relay corresponding to the units digit of the calling line.

Since it is assumed that the units digit of the calling line is No. 1, relay IULOI is operated over a circuit extending from (-l-) on tens digit No. 1 common conductor (above traced), make contact of relay LR, make contact of relay LO, common units digit No. 1 conductor, break contact of relay SW, winding of the No. 1 units marker relay IULOI, break contact of relay IULOI, conductor l2, break contact of relay IULOI), conductor '13,

` through the series circuit including break conthrough resistor 2RS, make contact and winding tacts of other IULO relays (not shown), break contact of relay IULO2, break contact of relay IULOI and resistor 2RS to Relay IULOI closes a locking circuit for itself from of relay IULOI and over the previously described circuit to on common umts digit No. 1 conductor. The units marker relays are interlocked 1n a manner similar to the tens marker relays to prevent the operation of more than one of these units marker relays at any one time in the event of simultaneous calls.

The operation of relay IULOI (or any other units marker relay) closes a circuit for operating allotter relay l ALG of the allotter illustrated i in Fig. 4, extending from (-1-), make Contact of the IULOI relay, conductor ALG, break contact of guard relay GD of the allotter, break contact of allotter relay IAL and Winding of the allotter group relay IALG to This operation of relay IALG assumes that the first line finder is idle and may thus be allotted for this call. The operation of relay I ALG (or any other ALG relay of the allotter) closes an obvious circuit for operating relay GD. The operation of relay GD transfers the above described circuit for relay IALG from the uppermost break contact of relay l AL to the middle upper break contact of relay l AL and a make contact of IALG for locking this latter relay operated.

It will be understood that the AL relay of a line finder is in its operated position as long as this finder is in use, thus extending the above operating circuit for the ALG relay to one of these relays which is associated with an idle line nder. The circuit for operating the AL relay of an associated line finder will be later described. At this point, however, it will be pointed out that any AL relay which is operated, establishes a locking circuit for itself by way of its upper winding for maintaining the AL relay operated until relay GD is released, as will later be described, thus preventing interference by the dropping out of a iinder while another finder is being allotted. Furthermore, the locking circuits for all AL relays, except the last, are completed through a normally closed break contact of the last allotter relay of the group, thus causing the nder links to be allotted in straight-forward rotation, even though an earlier nder of the group is released before all of the nders of the group become busy. This is because the release of an earlier nder does not permit the release of its associated AL relay as long as the last finder of the group is not in use.

With relays I TLOI and IULOI of the marker operated and with relay IALG of the allotter operated, all as previously explained, the line nder relays of the No. 1 line nder are operated for selecting the calling line, in this example tens finder relay TFI and units nder relay UFI because the tens and units digits of the calling line are both No. 1. The circuit for operating relay TFI of the allotted line nder may be traced from (-1-), break Contact of relay SW, make contact of relay ITLOI, conductor ITF, make Contact of allotter relay IALG and Winding of relay TFI to The circuit for operating units nder relay UFI may be traced from (1) break contact of relay SW, make contact of relay IULOI, conductor IUF, make contact of relay IALG and Winding of relay UFI to The operation of the tens and units nder relays (in this example relays TFI and UFI) extends the calling line to the rst selector repeater associated with the line finder used for this call. The extension of this line circuit to this first selector repeater closes a circuit for opertaing the calling bridge relay CB of the lirst selector repeater which extends from (-1-), upper winding of relay CB, break contact of answering bridge relay AB, break contact of link cut-01T relay LCO, link tip conductor LT, make contacts of relays UFI and TFI in series, tip line conductor T, calling substation, ring line conductor R, make contacts in series of relays TFI and UFI, link ring conductor LR, break contact of relay LCO, break contact of relay AB and lower winding of relay CB to This energizing circuit for relay CB maintains this relay operated until the dial impulses are transmitted. However, just previous to the extension of the calling line to the windings `of this relay, a preliminary operating circuit is closed for locally operating relay CB, which circuit is independent of the calling line and which may be traced from (-1-) resistor BRS, make contact of the operated ALG relay, link ring conductor LR and over the above described circuit to the lower Winding of relay CB. It Will`be understood that this preliminary impulse circuit is de-energized after sufcient time has been measured 01T to make sure that the calling line is connected to the windings of relay CB, by the release of the operated ALG relay as will be later explained.

The operation of relay CB of the rst selecto-r repeater closes a circuit for operating the slow acting relay SA which extends from (-1-), break contact of relay LCO, make contact of relay CB and winding of relay SA to The operation of relay SA closes an obvious circuit for operating its repeater relay SAP. The operation of relay SAP closes an obvious circuit for operating relay KP, this latter relay being for use particularly in connection with reverting calls, as will later be explained. The relay XP connects (-1-) to stick conductor STK for locking the operated line nder relays in their operated positions. The operation of relay SAP applies (-1) to link sleeve conductor LS for opera-ting relay CO of the calling line. This circuit may be traced from (-1-) on conductor LS, make contacts of relays UFI and TFI, inder sleeve conductor FS and winding of relay CO to The operation of relay CO (since relay LO is already operated) removes the battery bridge of the line circuit from the calling line, thus effecting the release of relay LR. The operation of relay CO opens up and releases relay ITLOI, While the release of relay LR opens up and releases relay IULOI The operation or relay SAP energizes the polarizing winding of polar relay POL, so that this relay is in condition for responding to reverse battery When the called party answers. Relay POL of course does not operate when its lower winding alone is energized. The operation of relay XP applies (-1-) to allotter conductor AL for operating relay IAL of the allotter, this circuit being traced from conductor AL through a make contact of the operated TF relay of the line nder and lower winding of relay IAL to The operation of relay IAL closes the above described locking circuit for its upper winding. The operation of relay lAL opens up the operating and locking circuits of relay IALG for releasing this relay, which in turn opens up and releases` relay GD.

The release of the marker relays ITLOI and IULOI restores the marker circuit to normal for use on a succeeding call and the release of relay GD of the allotter permits allotting the next link 'for the next succeeding call.

Referring to the rst selector repeater circuit, the operation of relay SA closes a circuit for operating the priming relay CX of the associated counting chain. This operation of relay CX prepares the counting circuit for receiving the impulses of the digits dialed into this circuit. The circuit for operating relay CX extends from (-1-) make contact of relay SA, conductor stick 1, break contact of counter release relay CRL, break contacts in series of counting relays C6 to CI inclusive and winding of relay CX to Referring to the layout of Fig. l, it will be noted that an originating call in suboice A is effective to associate the calling line with an idle rst selector repeater by means of the associated line nder, in the manner just described. An originating call must also cause the i'lrst selector repeater to select an idle two-way trunk to oil'ce B before any dialing operation is eiected. This is for the reason that a trunk circuit to oilce B is used throughout the connection if the call is directed to any station outside the subofce A. In the event that the call is for a station in subofce A, then when the first two digits ('74) are dialed the first selector repeater disassociates itself from the interolce trunk and is then directed by the third digit (No. 6) to the sixth level for selecting a connector, the connector then being responsive to the tens, units and stations digits of the called station.

With relays CB, SA, SAP and E@ of the first selector repeater operated as above described, a circuit is closed for operating relay TLOIB of the trunk marker. This relay is designated TLOIS because it is associated with the No. 16 selector of the complete group of 25. The circuit for operating relay TLOII:` extends from lowermost make contact of relay SAP, conductor 14, break contact of relay 2D4, conductor 15, lowermost make contact of relay SA, break contacts in series of the continuity spring combinations of relays STK, and BY, conductor TLOIB, winding of relay TLOI 6, break contact of relay TLO I 6 and break Contact of trunk marker common lockout relay TCLO to The operation of relay TLOIB closes, at its continuity make contact, a locking circuit for itself which includes the winding of relay TCLO, thus operating this latter relay for opening up the circuit to for all TLO relays of the group 'for preventing the operation of more than one of these relays at any one time.

The operation of relay 'I'LOIB closes a circuit for operating the allotter group relay of the trunk allotter associated with the idle assigned trunk. Assuming that trunk No. l is idle, the IALG relay will be operated over a circuit extending from lower-most make contact of relay TLOIG (or any other TLO relay which may have been operated), conductor 33, break contact of relay GD, break contact of relay IAL and winding of relay IALG to The operation of relay IALG (or any other ALG relay of this allotter) closes an obvious circuit for operating relay GD, which in turn transfers the circuit of relay IALG from its above described operating path to a locking path including a make contact of relay GD, break contact of relay IAL, make contact and winding of relay IALG to Since the operation of relay IALG marks the first two-way trunk to oice B as the one to be selected by the first selector repeater, it is now necessary to operate relays TMC and UCI of this selector repeater for extending the outgoing side of the selector repeater to the selected trunk circuit. The circuit for operating relay TMC may be traced from (-i) make contact of relay TLOIS, conductor 62, make contact of relay IALG, conductor 68 and winding of relay TMC to The circuit for operating relay UCI may be traced from make contact of relay TLOIS, conductor 63, make contact of relay IALG, conductor 64 and winding of relay UCI to The operation of relay TMC closes a circuit for operating stick relay STK of the first selector repeater, which may be traced from (-I) on the right hand terminal of the winding of relay TMC (above traced), make contact of relay TMC, conductor TMC STK and winding of relay STK to Relay STK closes a locking circuit for itself extending from (-1-), lower-most make contact of relay SAP, conductor 14, break contact of reday 2D4, conductor 15, lower-most make contact of relay SA, make contact and winding of relay STK to This locking circuit for relay STK is extended by way of its lower make contact, conductor I6 and lower-most break contact of relay 2D4 to conductor UMC STK and make contact of relay UCI to the winding of this relay for locking it in its operated position. Relay TMC is now locked in its operated position to the which locks relay STK, now extended back by way of conductor TMC STK and make contact of relay TMC to its winding.

The opening up of the break contact of the continuity combination of relay STK opens up conductor TLOI6 which extends to the winding of relay TLOI6 for releasing this relay. This also opens up and releases relay TCLO of the trunk marker, thus restoring the circuits of this marker to normal in preparation for the next call. The release of relay TLOIB removes from conductor 33 which effects the release of relay IALG and this relay in turn opens up and releases relay GD for preparing the trunk allotter for the next call. Before relay IALG is released, however, relay IAL of the trunk allotter is operated by the operation of relay SW (later explained) of the incoming selector associated with the selected trunk, this relay applying to conductor IALT'for operating relay IAL, which relay locks by way of its upper winding until the last allotter relay of the trunk allotter is operated.

The circuit for operating relay SW of the incoming selector may be traced from lowermost make contact of relay SAP of the first selector repeater, winding of relay X, conductor I4, make contact of relay UCI of the selector connector, make contact of relay TMC of the selector connector, sleeve conductor ST of the trunk circuit and winding of relay SW to The operation of relay SW of the incoming selector disconnects the tip and ring trunk conductors MT and MR. leading to oice B from the windings of relay CB of the incoming selector (since this incoming selector is not to be operated on this call) and connects these trunk conductors to the tip yand ring conductors TT and RT leading back to relay TMC of the selector connector and then through make contacts of this relay and make contacts of relay UCI to conductors I2 and I3. Conductor I2 may now be traced through the upper-most break contact of relay 2D4, conductor TI, upper winding of relay POL, impedance coil IMP, make contact of relay CB, conductor 'I8 and break contact of relay 2D4 to conductor I3, thus establishing a closed circuit across the tip and ring conductors of the two-way trunk to oice B. This prepares the circuits for receiving and repeating dial impulses. Relay IAL of the trunk allotter is operated when relay SW of the incoming selector is operated to mark this trunk busy, over the previously described circuit including conductor IALT.

Since the calling line in oce A is now con- 

